1. Field of the Invention
This invention relates generally to failsafe mechanisms and, more particularly, to a system and method for implementing a failsafe mode of operation with respect to a slave device.
2. Description of the Related Art
In applications where a critical function is being performed in a system (e.g. battery charging or fan control in portable computers), slave devices may perform monitoring functions. For example, a slave device may monitor the temperature associated with a particular subsystem to determine whether to turn on the system fans. Typically, monitoring slave devices depend on the host processor for sending setup and critical information associated with the particular functions being performed during system operation. If the host processor malfunctions or has overextended its resources, the critical information (e.g., a temperature limit) may not be sent to the monitoring device in a timely manner. Damage to the system could result if the monitoring device fails to receive such information, for example, a subsystem may overheat or a battery may be overcharged.
In some implementations, the monitoring device (e.g., the slave device), in addition to performing the monitoring functions associated with the critical operations being performed in the system, may send a check signal to the processor to determine if the processor is working properly. If the processor responds with the correct data, then this indicates to the monitoring device that the processor is operating properly. However, if the processor fails to respond or sends incorrect data, then the monitoring device resets the processor because this indicates that the processor is malfunctioning.
In other implementations, a system may include a watchdog timer to monitor the activity of a host processor. The watchdog timer is typically a counter that counts down from a particular time value. If the processor fails to reset the watchdog timer before it counts down to zero, the watchdog timer resets the processor since this is indicative that the processor is malfunctioning.